The typical natural products such as handmade soaps, creams, body oils, balms, can deteriorate over time. This impairment may be caused by oxidation of oils and / or by the formation of bacteria and fungus. The products which inhibit or retard these defects are antioxidants and preservatives.
Many have probably heard of or even seen a defect that occurs with the oils in general, oils for cooking. This defect is the rancidity of oil along the storage time, denoted by the characteristic smell of rancid oil spoils. This defect can occur even with soap crafted, it is rare but can occur with soap made with certain oils, such as grape seed oil and which have in their formulation a high value of superfatting above 8%. The rancidity is an oxidation process where the free radicals formed by the light and air attack the unsaturations present in polyunsaturated oils, such as grape oil.
In products with a reasonable amount of water, and in water based creams is very common the formation and growth of microorganisms which eventually spoil the product. In these cases it is always necessary to use some type of preservative. In anhydrous or products with very little water is usually not necessary this precaution.